Description
Description: Materials Science Program, Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627, USA. The thermal expansion coefficient is presented as the coupling
between heat energy and mechanical work. It is shown that when heat
and work are uncoupled then very unusual material properties occurs:
for example, acoustic p waves are not damped and heat is not
generated from mechanical motion. It is found that at pressures
defined by the bulk modulus divided by the Anderson–Grüneisen
parameter, then the thermal expansion coefficient approaches zero in
linear-elastic models. Very large pressures always reduce thermal
expansion coefficients; the importance of a very small or even
negative thermal expansion coefficient is discussed in relation to
physical processes deep in the core and mantle of Earth. Models of
the thermal expansion coefficients based on interatomic potentials
which are always relegated to isometric conditions preclude any
changes in volume due to temperature changes. However, it is known
that the pressures in the Earth are large enough to effectively
reduce thermal expansion coefficients to near zero which decouples
heat from mechanical work.

Summary
Is there a layer deep in the Earth that uncouples heat from mechanical work?